Page 87 - Science class 4

Quenching The Scientific Thirst
Quenching The Scientific Thirst
Quenching The Scientific Thirst
Quenching The Scientific Thirst
Quenching The Scientific Thirst
Quenching The Scientific Thirst
Quenching The Scientific ThirstQuenching The Scientific Thirst
Quenching The Scientific Thirst
Quenching The Scientific Thirst
force. What happens when Quenching The Scientific ThirstQuenching The Scientific Thirst
you throw a ball up into the
Force of gravity is active on an object
air? The ball goes up in the even when the object is at rest.
air and then falls back down.
It falls back down because the Earth has special attractive force called gravity
which pulls it down towards the Earth.
Friction
Friction
Friction
The force that slows down or stops a moving object

is called friction. Friction between car tyre and road
makes the car to move on road. Friction produces
when two objects come in contact with each other.

Take a toy train and move it on a smooth floor. Note
how much distance it will cover. Now, bring a toy

train in a garden. Try to move it on grass.

Again note how much distance it will cover. Does the toy cover long distance
than it did on a smooth surface? No! This is because a smooth surface has less

friction and a rough surface has more friction.

Some More ForcesSome More ForcesSome More Forces

Muscular Force
The force exerted by our muscles is called muscular

force. For example - you use your muscles to uplift the
load.

Magnetic Force

The force applied by the magnet is called magnetic force . For example : when
you put some iron nails near magnet, they start pulling towards magnet and

get stick to it.

Mechanical Force

The force applied with the help of tools is called mechanical force. For example
- you use a scissor to cut paper or you use an opener to open a bottle.

WORK AND MACHINES

How many times do you use the word ‘work’? The word ‘work’ is the most

commonly used word in our daily life. However, in Science, work has a very
precise meaning. Let us look at the following examples.